1. Field of the Invention
The present invention relates generally to a driving circuit; particularly, the present invention relates to a light-emitting diode (LED) driving circuit capable of decreasing the cost and enhancing efficiency.
2. Description of the Prior Art
In general, the conventional light-emitting diode (LED) driving circuit utilizes AC/DC power convertor to generate an input voltage, and the input voltage drives LEDs to generate light. In practical applications, the LED driving circuit includes a power supply module, wherein the power supply module controls current of the circuit, so that current amplitude crossing over the LEDs remains constant, and the brightness of the LEDs maintains constant.
Particularly, the conventional LED driving circuit further includes a plurality of switches and a plurality of comparators corresponding to the switches, wherein the switches are respectively coupled with corresponding comparators and LEDs. In addition, each comparator has a constant voltage and determines whether to transmit activating control signal to the switches according to the relation between the constant voltage and the input voltage. In practical applications, the conventional LED driving circuit controls the light-emitting result of driving the LEDs according to the activating condition of the switches. In other words, if more switches are driven to be activated, more LEDs generate light. However, in the circuit, because each switch has the comparator corresponding to the switch, the circuit requires lots of comparators, resulting in a complicated driving circuit and the increase in production cost.
In addition, please refer to FIG. 1; FIG. 1 is a schematic view showing the relation between the input current of the conventional LED and the current of the LED. As shown in FIG. 1, an input current curve 11 has full-wave rectification waveform, and an LED current curve 12 has sawtooth waveform. In other words, when the input voltage drives the LEDs to generate light, the LEDs waste some of input current, resulting in waste of power and reduction of cooling efficiency.
For the above reasons, it is an object how to design an LED driving circuit for enhancing efficiency and decreasing the cost.